Testing my route in controller with PHPUnit

I am using PHPUnit to test my registration api that I created in a controller. Function works fine but I don't know how to implement logic to test it via PHPUnit..

My code:

namespace Tests\AppBundle\Entity;

use PHPUnit\Framework\TestCase;

class UserTest extends TestCase
{

  public function testBasic()
  {
    // here I want to test my api with phpUnit
  }

}

And in my Controller I have a function that I need to implement:

 /**
 * @Route("/register", name="register")
 * @return \Symfony\Component\HttpFoundation\JsonResponse
 * @throws \Doctrine\Common\Annotations\AnnotationException
 */
public function testAction()
{
    $this->requirePostParams(['first_name', 'last_name]);

    $firstName = $this->data['first_name'];
    $lastName = $this->data['last_name'];

    $user = $this->get('app')->testIt($firstName, $lastName);

    return $this->success($response);
}